The general field of this invention is of alpha-numeric character coding keyboards. More specifically, this invention pertains to apparatus and methods for using a rectangular array of pushbuttons, such as the pad of buttons of a pushbutton telephone set, to generate and transmit alpha-numeric information.
The pushbutton telephone has long been recognized as a possibly convenient access terminal to a digital computer. Inventors have devised ways to use the limited number of buttons to allow the sending of alpha-numeric information over telephone lines to a distant computer.
U.S. Pat. No. 3,675,513 describes one such method. A telephone pushbutton dial is left unaltered and the labels normally appearing on the telephone set are used as an aid in determining how to generate a character. Two separate modes are required to generate alphabetic characters and numbers. The alphabetic mode and the numeric mode are generated respectively by three pushes of the asterisk (*) button and the octothorpe (-) button. In the numeric mode, the numbers of the buttons indicate the button to be pushed. In the alphabetic mode, a letter is generated by pushing the button a number of times equal to the numerical position in the three letter sequence in which the button is labeled.
Another way to generate alpha-numeric information, by using a pushbutton telephone set, was proposed in an article by Leon Davidson, Datamation, "A Pushbutton Telephone for Alpha-Numeric Input," April, 1966, pp. 27-29. This proposal left the telephone dial labels intact and described a method for generating letters by using the letters associated with the buttons in conjunction with the asterisk (*) and octothorpe (-) buttons. These buttons are on the left and right columns of the fourth row of an ordinary three column-four row pushbutton keyboard. A letter appearing in a three letter sequence is identified by pushing the left button to identify the left letter, the right button to identify a right letter, followed by pushing the button containing the desired letter. Both asterisk and octothorpe buttons are pushed in succession to identify a middle letter. If neither asterisk or octothorpe buttons are pushed, the digit would be indicated by pushing a button labeled with a number.
U.S. Pat. No. 3,381,276 disclosed a method of generating alpha-numeric information by using a pushbutton telephone set where two buttons are depressed simultaneously.
The disadvantage of the prior art attempts for using a small rectangular array of buttons, such as with a pushbutton telephone set, has been with the slowness and awkwardness of use. It is very difficult for the ordinary person to generate alphabetic text by first finding a letter to be generated on the buttons, remembering the code by which it will be generated, and going on to the next letter.
In addition to the inherent difficulties of remembering new sequential push codes, simultaneous push codes, etc., the number of symbols available for use on an ordinary pushbutton telephone keyboard is limited. For example, while all letters except the letters Q and Z and all the digits from zero through nine appear on the keyboard, there is no convenient way to generate other symbols normally appearing on a typewriter keyboard. Special symbols used in generating computer program listings are not available nor are symbols to provide back space, capital letters, etc.
It is therefore an object of this invention to provide methods and apparatus which will allow an ordinary user to use a small keyboard to generate alphanumeric information with little training and with reasonable speed.
It is another object of this invention to provide an increased number of symbols to the user than an ordinary pushbutton telephone keyboard provides, giving the user the ability to generate ordinary English text or special symbols used in generating computer program listings.